The present invention relates to flexible line trimming apparatus and, particularly, to a head for a flexible line trimming apparatus in which a flexible trimming filament or line segment may be inserted in the head and retained by a releasable clamping mechanism.
Rotary line trimmers are widely used for cutting or trimming grass, weeds and other vegetation in the upkeep of lawns. Line trimming apparatuses are typically characterized by a flexible, nylon trimming filament or xe2x80x9clinexe2x80x9d which is attached to a rotatable head of the apparatus. The line head is attached to a motor shaft which is rotated at high speeds, typically by trigger operation of a small gasoline engine or electric motor. When the line head is rotated, the rotating trimming filament serves as a cutting blade to cut grass, weeds or other vegetation.
After prolonged use of the apparatus, the cutting filament becomes worn and breaks, eventually requiring replacement. Accordingly, some line trimming apparatuses utilize a spool of the trimming filament or line which is incorporated in the whirling line head. The trimming filament is wound on the spool such that the filament can be dispensed from the spool as the rotating head is struck lightly against the ground. In other line trimming apparatuses, one or more short segments of trimming filament are attached to the line head for achieving the trimming function, and the trimming filaments are replaced by attaching replacement lengths of the trimming filament to the head. In both types of line trimming apparatus, the trimming filament typically extends from the line head through only one opening, and the edges of the opening engage the filament as the line head is rotated. After brief use of the apparatus, the edges tend to score the filament, causing premature breakage of the filament and requiring frequent and often difficult replacement of the filament in the head.
Line trimming apparatuses having heads of various design and including features for facilitating replacement of worn or broken trimming filaments, are well-known in the art. Patents of interest include U.S. Pat. Nos. 4,571,831; 5,303,476; 5,345,683; 5,758,424; 5,836,227; 5,887,348; and 5,896,666.
The present invention provides an improved head for a flexible line trimming apparatus.
A head for a line trimming apparatus according to this invention is characterized by a body including a filament channel which extends through the head and receives a trimming filament of selected length. The single, substantially linear trimming filament is releasably clamped in the filament channel and extends from opposite sides of the head to thereby double the cutting or trimming efficiency of the apparatus. The opposed ends of the filament channel are each characterized by generously curved filament contact and support walls which engage the filament during rotation of the head, to prevent excessively acute or sharp bending of the filament and thus, such construction of the head significantly enhances filament longevity.
The present invention also provides a head for a line trimming apparatus characterized by a body and a cover which are typically secured to a motor shaft of the apparatus and enclose a sliding filament clamp which receives a trimming filament of selected length and thickness.
In one embodiment the filament clamp is characterized by a pair of clamp arms which extend from a clamp base through a pair of adjacent walls of the body and define a filament channel therebetween which substantially bisects the body, and the trimming filament extends through the clamp arms in the filament channel and from the filament channel at opposite sides of the body. The filament clamp is normally biased in a clamping position in which the clamp arms press the trimming filament against one of the channel defining walls of the body, and the extending end portions of the clamped filament are capable of cutting or trimming weeds, grass or other vegetation as the head is rotated.
In another embodiment of a head in accordance with the invention, the filament clamp comprises spaced apart clamp arms which are engageable with a filament to forcibly urge the filament against one of the walls forming a filament receiving channel in the body. A separate actuator member having a digitally actuatable button formed thereon is engageable with the clamp to move the clamp away from forcible engagement with the filament to allow removal and replacement thereof. In both embodiments, the filament clamp can be moved to a release position in which it releases the trimming filament from forcible engagement with the body wall to facilitate removal and replacement of the trimming filament in the head, as needed.
In both embodiments of the invention, a spring biases a filament clamp in a clamping position in which the clamp arms press the trimming filament against one of the clamp walls of the body, such that the trimming filament is secured in the filament channel and the extending end portions of the filament are capable of cutting or trimming weeds, grass or other vegetation as the head is rotated. In addition to the bias exerted by the clamp spring, the weight of the filament clamp imparts centrifugal forces thereto which stabilizes it in the clamping position as the line head is rotated.
An object of this invention is to provide a head for a line trimming apparatus which utilizes a trimming filament segment which can be easily removed and replaced on the head, as needed.
Another object of this invention is to provide a head for a line trimming apparatus characterized by a body member and a cover which are attachable as an assembly to a motor shaft of the apparatus, and a filament clamp is disposed on the body for receiving and forcibly engaging a trimming filament of selected length and thickness.
Another object of this invention is to provide a head for a line trimming apparatus characterized by a filament channel which extends through the head and receives a trimming filament releasably clamped in a filament channel and extends from opposite sides of the head to double the cutting or trimming efficiency of the apparatus, and the ends of which filament channel are each defined by a generously curved contact or support wall which engages the filament during rotation of the head, to prevent excessive bending and premature scoring and wearing of the filament so as to significantly enhance filament longevity.
Those skilled in the art will further appreciate the above-mentioned features and advantages of the invention together with other important aspects thereof upon reading the detailed description which follows in conjunction with the drawings.